Process of casting malleable castings



Oct- 13, 1925. 1,556,642

W. H. SMITH PROCESS OF CASTING MALI-JEABLE GASTINGS Filed April I0, 1924A Wi w F III/11111111110101!!!\ Patented Oct. 13, 1525.

um'rl-zn STATES PATENT OFFICE.

WILLIAM H. SMITH, OF DEARBORN, MICHIGAN, ASSIGNOR TO FORD MOTOR COMPANY,

OF DETROIT, MICHIGAN, A CORPORATION OF DELAWARE.

PROCESS OF CASTING MALLEAIBLE CASTINGS.

Application filed April 10. 1924. Serial no. 705,409.

To all 'wkom z't may concern:

Be it known that I, WILLIAM H. SMITH, a citizen of the United States,residing at Dearborn, in the county of Wayne and State of Michigan, haveinvented certain new and useful Improvements in Processes of CastingMalleable Castings, of which the following is a specification, referencebeing had therein to the accompanying drawings.

Malleable gray iron castings when cast in metallic molds or dies, arefirst white iron, or chilled cast iron, and the combined carbon is thenconverted by special heat treatment into an uncombined, amorphouscondition, which treatment renders the castings malleable.

The usual method of producing die cast iron castings is to produce whiteiron castings which are then annealed at a high temperature, causing aconversion ofthe carbon content to an amorphous, uncombined condition,the castings being permitted to slowly cool. Essential conditions areproper control of temperature and time, the cooling being suflicientlydelayed to give proper annealing. The texture on malleability ofcastings cast in dies, is dependent upon the rate 0 temperature dropthrough the critical range of cooling, which is about 1200 F. The commonpractic involves several independent steps and separate annealing andhandling, with difliculty arising from inaccurate control of time andtemperature of cooling, oxidization, and required skill in producing auniform product.

This invention relates to a process or method for producing malleablegray iron castings, and its object is to simplify methods, increaseproduction, insure uniform product, and provide certain other new anduseful features, all as hereinafter more fully described,.th e inventionconsisting in providing a method wherein the operation of cooling themetal to give the desired malleability is introduced into the castingopera tion and accurately controlled as to time and temperature bycontrolling the transfer of heat from casting. to cooling medium, and

further consists in certain other new and useful features, all ashereinafter more fully described, reference being had to theaccompanying drawing illustrative of one means whereby the methodembodying the invention may be performed.

In the drawing,

Figure l is a plan view of a mold construction shown for the purposeofillustrating the method embodying the invention;

Fig. 2 is a longitudinal vertical section through the same; 3

- Fig. 3 is a transverse section substantially upon the line 33 of Fig.2, and

Fig. 4 is a sectional perspective detail of a casting cast in'the mold.

The present invention contemplates the casting of molteniron in ametallic mold or die, the temperature of whichv is raised to a properdegree of heat above 500 F. and

' maintained at such temperature by a suitable heat conducting fluidtomaintain a temperature equilibrium between the metal and .said heatingmedium, whereby the proper time in the fall of the temperature of thecasting is secured to produce malleability of the casting. I

Formerly it has been deemed necessary to cast the metal and then reheatthe casting to anneal the iron and produce malleability. The presentinvention contemplates the casting of the metal in dies and controllingthe temperature of these dies to regulate the rate of coolingof the castmetal and produce malleability thereof. c-

As illustrative of a die construction which may be employed in thecarrying out of the presentmethod or process, a two part die formed of asuitable material, preferably metal, is provided, the confronting facesof which parts are formed to give the desired configuration to thecasting. These two parts 1 and 2 of the die or mold preferably togetherform a wall 4 which separates chambers 3, each die part forming a partof said wall andthe chambers forming receptacles or passages for a fluidbody 5 which is thus in direct contact with the die or mold wall. Thefluid is maintained, in any suitable manner, at the proper temperatureto maintain a certain heat ratio between die walls have the desiredstructure without higher heating. This fluid which may be maintained ata uniform high temperature by the heat transferred thereto by the moltenmetal in casting or otherwise, may be Cl} culated in any suitable mannerif found desirable, to graduallv carrv of? the heat imparted thereto bythe metal through the cooled and at the same time maintained at theproper temperature to prevent too rapid cooling of the casting, bymaintaining a body of molten tin at a temperature of 500 F.

, or over and in direct contact with the walls 4 of the metallic diewhich walls form the two parts of the die or mold proper, between Vwhich the casting is formed. As tin is one 5 of the metals having a highheat conductivity and which can be maintained fluid at at the same timewill have the proper egree a this comparatively low temperature (500F.), the rate of drop in temperature of the feasting through itscritical stage, is accurately controlled and proper malleability secureddur' the casting operation, and at the same time, the conductivity ofthe molten tin is such that the mold will be cooled, or its temperatureprevented from rising to such a point that in ury to the mold'willqresult therefrom. Metal molds may therefore be employed and willbe protected against rapid disintegration so that they may be usedthrough long periods of time. The conductivity; of the molten tin is nothowever so great as to cause a too rapid cooling of the casting but willabsorb suflicient heat to provide the desired retardation of drop intemperature as the metal passes through its critical stage ofapproximately 1200 F. and give proper annealing, but sufficiently rapidto prevent the'forma'tion of graphite.

, Any fluid cooling-medium may be employed which will retain sufiicientheart to properly retard cooling of the castin and 6f heat conductivityto cool the casting and mold, but it has been found that molten tin isvery efficient for the purpose and preferable.

In the drawing, a mold has been shown for the purpose of illustratingthe method embodying the present invention, but it will be understoodthat an I suitable form or construction of mold w ich will rovide formaintaining contact of the cooling medium with the mold wall may beemployed, suitable provision being made for separating the die moldparts land 2 to discharge the castings, as by making the partsrelatively movable upon suitable guides 6 or the like and providing anysuitable means, as a screw 7 for moving relatively theboxes orreceptacles 8 forming the chambers 3, so that the formed castings 9 maybe discharged from the die or mold.

By this method the cooling of the cast metal may be very accuratelycontrolled and time regulated to produce a uniform product, andreheating of the castings is obviated, due to this acurate and delayedcooling of the metal within. the mold or die in which the casting isformed. Oxidization is also prevented as all air is excluded from thecasting by its inclosure within the die.

The method embodying the present invention may be modified within thescope of the appended claim, and such modifications are contemplated.

What I claim is The method of casting malleable castings which consistsin providin a mold, introducing molten metal into t e mold to form acastmg, and in maintaining a body of tin in fluid state in contact withthe mold walls. In testimony whereof I alfix my signature.

WILLIAM SMITH.

